221506213 has 2 divisors, whose sum is σ = 221506214. Its totient is φ = 221506212.

The previous prime is 221506151. The next prime is 221506217. The reversal of 221506213 is 312605122.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 198302724 + 23203489 = 14082^2 + 4817^2 .

It is a cyclic number.

It is not a de Polignac number, because 221506213 - 2²¹ = 219409061 is a prime.

It is equal to p_12200854 and since 221506213 and 12200854 have the same sum of digits, it is a Honaker prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (221506217) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 110753106 + 110753107.

It is an arithmetic number, because the mean of its divisors is an integer number (110753107).

Almost surely, 2^221506213 is an apocalyptic number.

It is an amenable number.

221506213 is a deficient number, since it is larger than the sum of its proper divisors (1).

221506213 is an equidigital number, since it uses as much as digits as its factorization.

221506213 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 720, while the sum is 22.

The square root of 221506213 is about 14883.0847944907. The cubic root of 221506213 is about 605.0556267865.

The spelling of 221506213 in words is "two hundred twenty-one million, five hundred six thousand, two hundred thirteen".